Opportunity, also known as MER-B (Mars Exploration Rover – B) or MER-1, is a roboticrover active on Mars since 2004.[2] Launched on July 7, 2003 as part of NASA's Mars Exploration Rover program, it landed in Meridiani Planum on January 25, 2004, three weeks after its twin Spirit (MER-A) touched down on the other side of the planet.[7] With a planned 90 sol duration of activity (slightly more than 90 earth days), Spirit functioned until getting stuck in 2009 and ceased communications in 2010, while Opportunity was active as of June 10, 2018 when a dust storm forced it to hibernation. It has operated 5328 sols since landing, having exceeded its operating plan by 14 years, 269 days (in Earth time). Opportunity has operated for over 55 times its designed lifespan. As of June 10, 2018 when contact was lost, the rover had traveled a distance of 45.16 kilometers (28.06 miles).[6]

Mission highlights include the initial 90 sol mission, finding extramartian meteorites such as Heat Shield Rock (Meridiani Planum meteorite), and over two years studying Victoria crater. The rover survived dust-storms and in 2011 reached Endeavour crater, which has been described as a "second landing site".[8]

Due to the 2018 dust storms on Mars, Opportunity ceased communications on June 10 and entered hibernation on June 12, 2018. It was hoped it would reboot once the atmosphere cleared[9], but it did not, suggesting either a catastrophic failure or that a layer of dust has covered its solar panels. NASA hopes to reestablish contact with the rover, citing a windy period that could potentially clean off the solar panels of the rover.[10]

The primary surface mission for Opportunity was planned to last 90 sols (92 Earth days). The mission has received several extensions and has been operating for 5474 days since landing. An archive of weekly updates on the rover's status can be found at the Opportunity Update Archive.[11]

From its initial landing, by chance, into an impact crater amidst an otherwise generally flat plain, Opportunity has successfully investigated soil and rock samples and taken panoramic photos of its landing site. Its sampling allowed NASA scientists to make hypotheses concerning the presence of hematite and past presence of water on the surface of Mars. Following this, it was directed to travel across the surface of Mars to investigate another crater site, Endurance crater, which it investigated from June – December 2004. Subsequently, Opportunity examined the impact site of its own heat shield and discovered an intact meteorite, now known as Heat Shield Rock, on the surface of Mars.

From late April to early June 2005, Opportunity was perilously lodged in a sand dune, with several wheels buried in the sand. Over a six-week period Earth-based physical simulations were performed to decide how best to extract the rover from its position without risking a permanent immobilization of the valuable vehicle. Successful maneuvering a few centimeters at a time eventually freed the rover, which resumed its travels.

Opportunity was directed to proceed in a southerly direction to Erebus crater, a large, shallow, partially buried crater and a stopover on the way south towards Victoria crater, between October 2005 and March 2006. It experienced some mechanical problems with its robotic arm.

In late September 2006, Opportunity reached Victoria crater and explored along the rim in a clockwise direction. In June 2007 it returned to Duck Bay, its original arrival point; in September 2007 it entered the crater to begin a detailed study. In August 2008, Opportunity left Victoria crater for Endeavour crater, which it reached on August 9, 2011.[12]

Here at the rim of the Endeavour crater the rover moved around a geographic feature named Cape York. The Mars Reconnaissance Orbiter had detected phyllosilicates there, and the rover analyzed the rocks with its instruments to check this sighting on the ground.
This structure was analyzed in depth until summer 2013. At May 2013 the rover was heading south to a hill named Solander Point.

Opportunity's total odometry as of June 27, 2016 (sol 4417) was 42.85 km (26.63 mi), while the dust factor is 0.725.
[13] Since January 2013, the solar array dust factor (one of the determinants of solar power production) varied from a relatively dusty 0.467 on December 5, 2013 (sol 3507) to a relatively clean 0.964 on May 13, 2014 (sol 3662).[14]

In December 2014, NASA reported that Opportunity was suffering from "amnesia" events in which the rover fails to write data, e.g. telemetry information, to non-volatile memory. The hardware failure is believed to be due to an age-related fault in one of the rover's seven memory banks. As a result, NASA had aimed to force the rover's software to ignore the failed memory bank,[15] however amnesia events continued to occur which eventually resulted in vehicle resets. In light of this, on Sol 4027 (May 23, 2015), the rover was configured to operate in RAM-only mode, completely avoiding the use of non-volatile memory for storage.[16]

As of May 2018 into the early days of June, Opportunity was still functioning on the surface of Mars, and engaged in further scientific exploration.[17]

In early June 2018, a large global-scale dust storm developed and within a few days the rover's solar panels were not generating enough power to maintain communications, with last contact on June 10, 2018. NASA stated they did not expect to resume communication until after the global dust storm subsided,[18] but the rover kept silent even after the storm ended in early-October,[18] suggesting either a catastrophic failure or a layer of dust covered its solar panels.[19] The team remains hopeful that a windy period between November 2018 and January 2019 may clear the dust from its solar panels, as has happened before.[19] On January 8, 2019, dust storm activities were detected near the rovers site which could possibly wake it up after 7 months of silence.[20]

HiRise image from MRO, was laid over 3-D topographic map of the terrain, with 5-fold vertical exaggeration; view looking west on to Perseverance Valley on the western rim of Endeavour crater (February 15, 2018)[21]

The scientific objectives of the Mars Exploration Rover mission are to:[22]

Determine the distribution and composition of minerals, rocks, and soils surrounding the landing sites.

Determine what geologic processes have shaped the local terrain and influenced the chemistry. Such processes could include water or wind erosion, sedimentation, hydrothermal mechanisms, volcanism, and cratering.

Perform calibration and validation of surface observations made by Mars Reconnaissance Orbiter instruments. This will help determine the accuracy and effectiveness of various instruments that survey Martian geology from orbit.

Search for iron-containing minerals, identify and quantify relative amounts of specific mineral types that contain water or were formed in water, such as iron-bearing carbonates.

Characterize the mineralogy and textures of rocks and soils and determine the processes that created them.

During the next two decades, NASA will continue to conduct missions to address whether life ever arose on Mars. The search begins with determining whether the Martian environment was ever suitable for life. Life, as we understand it, requires water, so the history of water on Mars is critical to finding out if the Martian environment was ever conducive to life. Although the Mars Exploration Rovers do not have the ability to detect life directly, they are offering very important information on the habitability of the environment in the planet's history.

Opportunity (along with its twin, Spirit) is a six-wheeled, solar-powered robot standing 1.5 meters (4.9 ft) high, 2.3 meters (7.5 ft) wide, and 1.6 meters (5.2 ft) long and weighing 180 kilograms (400 lb). Six wheels on a rocker-bogie system enable mobility. Each wheel has its own motor, the vehicle is steered at front and rear and is designed to operate safely at tilts of up to 30 degrees. Maximum speed is 5 centimeters per second (2.0 in/s) although average speed is about a fifth of this (0.89 centimeters per second (0.35 in/s)). Both Spirit and Opportunity have pieces of the fallen World Trade Center's metal on them that were "turned into shields to protect cables on the drilling mechanisms".[23][24]

Solar arrays generate about 140 watts for up to fourteen hours per Martian day (sol) while rechargeable lithium ion batteries store energy for use at night. Opportunity's onboard computer uses a 20 MHz RAD6000 CPU with 128 MB of DRAM, 3 MB of EEPROM, and 256 MB of flash memory. The rover's operating temperature ranges from −40 to +40 °C (−40 to 104 °F) and radioisotope heaters provide a base level of heating, assisted by electrical heaters when necessary.[25] A gold film and a layer of silica aerogel provide insulation.

Communications depends on an omnidirectional low-gain antenna communicating at a low data rate and a steerable high-gain antenna, both in direct contact with Earth. A low gain antenna is also used to relay data to spacecraft orbiting Mars.

Examples of watt-hours per sol collected by the rover.[27][clarification needed] The rover uses a combination of solar cells and a rechargeable chemical battery.[28] This class of rover has two rechargeable lithium batteries, each composed of 8 cells with 8 amp-hour capacity.[29] At the start of the mission the solar panels could provide up to around 900 watt-hours to recharge the battery and power system in one Sol, but this can vary due to a variety of factors.[28] In Eagle crater the cells were producing about 840 watt-hours, but by Sol 319 in December 2004, it had dropped to 730 watt-hours.[30]

Like Earth, Mars has seasonal variations that reduce sunlight during winter. However, since the Martian year is longer than that of the Earth, the seasons fully rotate roughly once every 2 Earth years.[31] By 2016, MER-B had endured seven Martian winters, during which times power levels drop which can mean the rover avoids doing activities that use a lot of power.[31] During its first winter power levels dropped to under 300 watt-hours per day for two months, but some later winters were not as bad.[31]

Another factor that can reduce received power is dust in the atmosphere, especially dust storms.[32] Dust storms have occurred quite frequently when Mars is closest to the Sun.[32] Global dust storms in 2007 reduced power levels for Opportunity and Spirit so much they could only run for a few minutes each day.[32] Due to the 2018 dust storms on Mars, Opportunity entered hibernation mode on June 12,[33][34] but it remained silent after the storm subsided in early-October.[18]

Opportunity's launch was managed by NASA's Launch Services Program. This was the first launch of the Delta II Heavy. The launch period went from June 25 to July 15, 2003. The first launch attempt occurred on June 28, 2003, but the spacecraft launched nine days later on July 7, 2003 due to delays for range safety and winds, then later to replace items on the rocket (insulation and a battery). Each day had two instantaneous launch opportunities. On the day of launch, the launch was delayed to the second opportunity (11:18 p.m. EDT) in order to fix a valve.[35]

In late December 2004, Opportunity reached the impact site of its heat shield, and took a panorama around Sol 325.[36]

Area around the heat shield, including the resulting shield impact crater. The heat shield was released before the rover landed and impacted the surface on its own, and the rover later roved to the impact site. Near this location it discovered the first meteorite found on Mars, Heat Shield Rock

Heat Shield Rock turned out to be the first meteorite discovered on Mars

Opportunity has provided substantial evidence in support of the mission's primary scientific goals: to search for and characterize a wide range of rocks and soils that hold clues to past water activity on Mars. In addition to investigating the water, Opportunity has also obtained astronomical observations and atmospheric data.

On July 28, 2014, it was announced that Opportunity, having traversed over 40 km (25 mi), had become the rover achieving the longest off-world distance, surpassing the previous record of 39 km (24 mi) on the Moon by Lunokhod 2.[39][40]

On March 24, 2015, NASA celebrated Opportunity having traveled the distance of a marathon race, 42.195 kilometers (26.219 mi), from the start of Opportunity's landing and traveling on Mars.[41]

In March 2016, while trying to reach target on the slope of Marathon Valley in Cape Tribulation, the Mars rover attained a slope of 32 degrees, the highest angle yet for the rover since its mission began. This was so steep that dust that had accumulated on its top panels began to flow downward.[42]

Highest elevation

Opportunity's view from the top of Cape Tribulation on the rim of Endeavour Crater, January 22, 2015.

On Sol 3894 (Jan. 6, 2015) Opportunity reached the summit of "Cape Tribulation," which is 443 feet (135 meters) above "Botany Bay" level and the highest point yet reached by the rover on western rim of Endeavour Crater according to NASA.[18]

The rover can take pictures with its different cameras, but only the PanCam camera has the ability to photograph a scene with different color filters. The panorama views are usually built up from PanCam images. As of February 3, 2018, Opportunity had returned 224,642 pictures.[43][44]

Panorama taken on the rim of Erebus crater. The rover's solar panels are seen on the lower half (December 5, 2005).

Panorama of the rim of Endeavour crater from Cape Tribulation (January 22, 2015).

Panorama of Spirit of St. Louis crater, a shallow crater about 34 meters (110 ft) long and 24 meters (80 ft) across. In its center is Lindbergh Mound, about 2 to 3 meters (yards) high. (annotated; false color; May 2015).[46]

"Blueberries" (hematite spheres) on a rocky outcrop at Eagle Crater. Note the merged triplet in the upper left.

"Newberries": This view displays an area about 6 centimeters across. It was taken at an outcrop named "Kirkwood" at the Cape York on the rim of Endeavour crater on Mars. The spheres seen here are about 3 millimeters in diameter. The Microscopic Imager took this image at the 3064 sol.

An example of a rover traverse map featuring a line showing path of the rover, and mission sols, which are Mars days counted from its landing and typical of Mars surface mission time reporting. Topographic lines and various feature names are also common

Opportunity arrives at Endeavour crater

Opportunity traverse map, from Sol 405 to 528 (2005)

Opportunity traverse map, from sol 1 (2004) through sol 2055 (2009)

Annotated Opportunity traverse map as of December 8, 2010 (Sol 2442)

Annotated Opportunity traverse map as of June 11, 2014 (Sol 3689)

Opportunity's traverse on Cape York from Sol 2678 to Sol 3317 with some additional annotations of the main features.